1. Field of Invention
This invention is directed to fluid ejection devices. In particular, this invention is directed to methods for attaching fluid containers to fluid ejectors in fluid ejection devices.
2. Description of Related Art
Inkjet printing devices have gained prominence in printing as a result of their capabilities in performing quality, economical color and monochromatic printing. Inkjet printing devices include, but are not limited to, piezoelectric inkjet printing devices and thermal inkjet printing devices. Piezoelectric inkjet devices eject ink from a nozzle by mechanically generating pressure to deform an ink chamber. Thermal inkjet devices eject ink by energizing a heater element to vaporize ink.
In such inkjet printing devices, a die module, which acts to eject ink onto a recording medium, is joined to an ink manifold. That is, ink is supplied from the ink manifold to the die module via an ink supply interface between the ink manifold and the die module. The ink supplied to the die module is then ejected from one or more fluid passages in the die module.
Various methods are known for attaching the ink manifold to the die module. For example, the ink manifold and the die module can be sealed together using an adhesive. Other methods of attaching the ink manifold to the die module are also known. Such methods include providing an organic material between the ink manifold and the die module and sealing the three components together by ultrasonic welding. Also, the ink manifold and the die module could be sealed together by conventional heat staking methods.
A further method of sealing an ink manifold to a die module is disclosed in U.S. Pat. No. 6,460,965, which is incorporated herein by reference in its entirety. This method involves interposing an elastic member between the ink manifold and the die module and applying pressure to hold the seal. Pressure can be applied using bolts.
The above described methods of sealing an ink manifold to a die module have various deficiencies. For example, the use of adhesives requires that the amount of adhesive used and the positions of the ink manifold and die module be strictly managed during assembly. Controlling these aspects of manufacture increases cost and time of manufacture, while failure to control them can have adverse effects on print quality of the resulting printing device. Also, in the instance of heat cured adhesives, applied thermal energy can adversely affect the integrity of the adhered parts, again resulting in reduced print quality.
Some methods, such as the method disclosed in U.S. Pat. No. 6,460,965, are deficient in that they do not permit precise control over the distance between the ink manifold and the die module and/or the pressure with which the ink manifold and die module are joined. Sealing ink manifolds to die modules by ultrasonic welding or conventional heat staking also present similar difficulties. For example, both ultrasonic welding and heat staking introduce mechanical and thermal stresses that can adversely affect printing performance in the resulting printing devices. In addition, conventional heat staking methods do not allow precise control over the distance between the ink manifold and the die module and/or the pressure with which the ink manifold and die module are joined.
The difficulty in managing accurate position and/or pressure with conventional heat staking arises due to the interface between the heat staking material and the substrate that is being “staked.” As shown in FIG. 1, a thermoplastic heat stake 11 is used to stake an object (not shown) to a metal substrate 12. The heat stake 11 is inserted into an aperture 13 in the substrate 12. So that the heat stake 11 will fit into the aperture 13, the heat stake 11 has a diameter that is smaller than the diameter of the aperture 13. This difference in diameter between the heat stake 11 and the aperture 13 results in a first gap 14 between the heat stake 11 and an inner surface of the aperture 13.
When the object and the substrate 12 have been assembled with an end of the heat stake 11 protruding through the aperture, heat energy is applied to deform that end. The deformed end of the heat stake 11 prevents the heat stake 11 from being removed from the aperture 13, and thus binds the object to the substrate 12. However, after application of thermal energy ceases, the heat stake 11 cools unevenly. The portions of the heat stake 11 in contact with the substrate 12 cool more quickly than other parts of the heat stake 11. As a result, the portions of the heat stake 11 in contact with the substrate 13 tend to pull away from the substrate 12, leaving a second gap 15. The second gap 15 results in a reduction of the applied pressure holding the object to the substrate 13. This reduced pressure, in turn, causes a reduction in the friction between the heat stake 11 and the substrate 12 that allows the heat stake 11 to move in a direction normal to the direction in which the object and the substrate 13 are attached in the space left by the first gap 14. Accordingly, the presence of the first and second gaps 14, 15 permits play between the object and the substrate 12 after attachment is complete. This play is one of the causes of imprecise control of position and/or pressure between the staked elements.